Question: Ashley is 3 years older than Omar. Eight years ago, Ashley was 4 times as old as Omar. How old is Ashley now?
Explanation: We can use the given information to write down two equations that describe the ages of Ashley and Omar. Let Ashley's current age be $a$ and Omar's current age be $o$ The information in the first sentence can be expressed in the following equation: $a = o + 3$ Eight years ago, Ashley was $a - 8$ years old, and Omar was $o - 8$ years old. The information in the second sentence can be expressed in the following equation: $a - 8 = 4(o - 8)$ Now we have two independent equations, and we can solve for our two unknowns. Because we are looking for $a$ , it might be easiest to solve our first equation for $o$ and substitute it into our second equation. Solving our first equation for $o$ , we get: $o = a - 3$ . Substituting this into our second equation, we get the equation: $a - 8 = 4($ $(a - 3)$ $ -$ $ 8)$ which combines the information about $a$ from both of our original equations. Simplifying the right side of this equation, we get: $a - 8 = 4a - 44$ Solving for $a$ , we get: $3 a = 36$ $a = 12$.